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You are right. There are two things going on here: 1. They added background noise to the actual calls to let people know they other end wasn't disconnected.
by darkarmani 14y ago
You are right. There are two things going on here:
1. They added background noise to the actual calls to let people know they other end wasn't disconnected. The clarity got too good and people couldn't tell they were still connected. Fun fact: PCM - g.711 - is 64-kbits - hence max modem speed.
2. Dialing used to use in-band signalling and the tone lets you know you can dial (phreakers could use this to get free calls). When the dial tone ends, you know that your call is going through.
- akira2501 14y agoThe dial tone actually ends after the first digit is dialed. However, this is a significant digit, especially for older equipment. If you pressed 0, you would get the operator immediately. No phone numbers could begin with zero. If you pressed 1, you would be connected to a long distance trunk and an area code would then be expected. No local prefixes could begin with 1. If you pressed any other number it was a local call. Also, on analog networks, maximum modem speed was 56kbps. 64k was the theoretical maximum, but the FCC placed limits on the amount of power you could have in certain frequency bands on the line -- hence 56k was the maximum speed. On a purely digital network, like ISDN, you could receive 64kbps on each channel.